1. Field of Invention
This invention relates generally to filter devices and, more particularly to filters using scrapers or similar devices for removing particulates from a filter screen or other surface.
2. Description of Related Art
It is well-known that the mechanical cleaning of a filter surface can be accomplished by having a brush or scraper drag along, or be slightly spaced from, the filter surface where deposits have accumulated. In certain configurations, the brush or scraper is mounted at one end between two walls but with a significant portion of the brush or scraper projecting beyond the walls. Such configurations are shown in U.S. Pat. Nos. 148,557 (Gillespie et al.); 556,725 (Farwell); 740,574 (Kohlmeyer) and 793,720 (Godbe). In conventional filter systems, the particulate contaminants are driven off the filter surface and are deposited in a hopper or tank along with some of the fluid being filtered.
Scraper edges are prone to wear over time and therefore it is necessary to periodically adjust the relative position of the scraper edge with the filter surface. In some cases, it is desirable to make such adjustments without compromising or breaking the pressure boundary in the system being filtered by opening a hatch or access panel to reach the filter. This may become more complicated where such scrapers are used with filter assemblies for cleaning fuel oil in ships (see for example, U.S. Pat. Nos. 6,177,022 (Benenson, Jr. et al.); 6,517,722 (Benenson, Jr. et al.); 6,821,444 (Benenson, Jr., et al.)) because the fuel oil system is a critical system and as such the filter assemblies therein cannot be removed from service or otherwise opened for scraper adjustment.
Moreover, prior to placing the filter into service it often is necessary to initially set the position of the scraper edge a preset distance relative to the filter surface. It is desirable or beneficial to be able to provide this latter function without removal of any components, e.g., inspection port cover, of the filter system.
Laing et al. U.S. Pat. No. 7,364,662, assigned to the assignee of the present application, discloses a relatively complex, externally adjustable scraper arrangement whereby an inspection cover closes an inspection port and external adjustment tie rods are employed to transversely adjust the position of the scraper blades relative to the outer surface of a strainer surface. In the Laing et al. '662 construction, a separate wedge member is employed as part of the adjusting system to provide a balanced loading on the scraper blade, regardless of the direction of rotation of the filter assembly.
U.S. Pat. No. 740,574, issued to Kohlmeyer on Oct. 6, 1903, also discloses an adjustable scraper system which can be externally adjusted from outside of the chamber carrying rotating filter elements. The arrangement employed in the Kohlmeyer construction is relatively complex.
Steiner et al. U.S. Pat. No. 5,595,655 discloses a system for adjusting a scraper member (e.g. 108) by actuation of spaced apart bolts 115 designed to engage scraper plate 119 captured between the scraper 108 and shoe 114 (see FIGS. 2-4). The Steiner et al. system does not include any provision for backing the scraper blade off of the strainer surface. In other words, the system is only designed to move the scraper blade closer to the strainer surface to thereby permit adjustment of the scraper blade necessitated by wear of the blade. Moreover, the adjusting mechanism is located internally of the outer strainer housing. Therefore, external adjustment of the scraper blade cannot be achieved.
Thus, there remains a need and/or desire for a simple and reliable system permitting either initial adjustment or periodic adjustment of the scraper position in a filter assembly without the need to have access to the scraper/filter interface and without having to depressurize the filter assembly. It is to such a simplified system that the present invention relates.
All references cited herein are incorporated herein by reference in their entireties.